Field of the Invention
The present invention relates to a clutch structure for a vehicular power train.
Japanese Patent Application First Publication No. 62-288753 discloses a vehicular power train, including two multiple disc clutches within a clutch drum. One of the multiple disc clutches includes a set of multiple discs and a generally cylindrical piston forcing the set of multiple discs to be engaged with each other. The piston has projections and slots arranged circumferentially alternately. The other of the multiple disc clutches includes a set of multiple discs and a back-up plate for retaining the set of multiple discs. The multiple discs and the back-up plate have on radial outer peripheries thereof teeth engaged with the projections and slots of the piston of the one multiple disc clutch. The piston also has, on radial inner peripheries of the projections, grooves provided for mounting a snap ring for retaining the back-up plate.
It is an object of the present invention to provide a clutch structure for a vehicular power train that is capable of preventing a stress, caused when the piston forces an opposed disc, from concentrating on a portion of a piston that surrounds the groove for mounting a snap ring. This serves to improve retention of the snap ring at the groove and enhances the performance of the clutch.